The present invention relates to methods of enhancing fracturing stimulation in subterranean formations using in situ foam generation and pressure pulsing.
Subterranean wells (such as hydrocarbon producing wells, water producing wells, and injection wells) are often stimulated by hydraulic fracturing treatments. In hydraulic fracturing treatments, a viscous treatment fluid is pumped into a portion of a subterranean formation at a rate and pressure such that the subterranean formation breaks down and one or more fractures are formed. Typically, particulate solids, such as graded sand, are suspended in a portion of the treatment fluid and then deposited in the fractures. These particulate solids, or “proppant particulates,” serve to prevent the fractures from fully closing once the hydraulic pressure is removed. By keeping the fracture from fully closing, the proppant particulates aid in forming conductive paths through which fluids may flow.
Traditional treatment fracturing fluids require substantial amounts of an aqueous base fluid to be introduced into the formation, often diluting treatment fluids and impairing hydrocarbon flow due to formation fluid retention. Traditional treatment fracturing fluids may also damage the formation by reducing its permeability to hydrocarbons due to fluid-induced swelling of the formation. Thus, achieving adequate penetration of a subterranean formation, particularly in low pressure and fluid sensitive formations, using traditional hydraulic treatment fluids is often difficult because efficient fracture creation or propagation requires high-quality fluid loss control and minimal damage to the formation.
Foamed treatment fluids have been used to overcome some of the problems related to traditional treatment fluids. As used herein, the term “foam” refers to a two-phase composition having a continuous liquid phase and a discontinuous gas phase. Foamed treatment fluids permit reduction in the amount of aqueous base fluid required. Foamed treatment fluids also tend to have superior fluid loss control properties. However, the effectiveness of foamed treatment fluids is dependent upon the quality of the foam (e.g., the quality of gas phase). The gas phase of foamed treatment fluids can easily collapse or breakdown in conditions present in subterranean formations, such as compressive stress, temperature, salinity, acidity, and the presence of oils, for example. Collapsed foamed treatment fluids are represented only by their liquid phase. Therefore, in fracturing operations, the liquid phase of a collapsed foamed treatment fluid may damage or leak into the fracture face, just like traditional treatment fluids. Therefore, a method of creating in situ foam generation for propagating fractures in a subterranean formation may be of benefit to one of ordinary skill in the art.